Dual Station Coolant Temperature Sender

Hi, All

Our 2004 Nordic Tug 37 is the flybridge model with two helm stations. The instrumentation is VDO. It has a Cummins 6BTA 330. We are the third owner having purchased the boat in early-2017.

The pre-purchase engine inspection recommended replacement of the temp sender. This was done by the PO. The replacement part was Cummins 3613547 as per the detailed parts list and manufactured in 2014. The old sender was retained on board; from the paint on it, it appears to be the original install. It has a 1/2 inch NPT and a Bosch connection.

Subsequently, the gauges at both stations would never read over 130F. The initial step was to replace the thermostat - no change. Using a temp gun, it was established that the coolant temp was reaching the right levels 180/185. The suggestion was a bad ground in the wiring, some issues were found and corrected - no change.

Further research established that dual station VDO gauges require a dual station sender. VDO has two versions available, one is 1/4 NPT the other 3/8. Cummins does not supply a dual station sender for this engine.

Nordic Tug's input has been requested, no clarification so far; though it appears they would receive the engine from Cummins with the sender already installed.

This suggests that the temp gauge has always under-read. And that all Nordic Tug 37 fly-bridge models have the same issue. Really??

Any ideas appreciated - and especially where I can get a dual station 1/2 inch NPT Bosch connection sender!

Of course, the next question is whether the over-heat alarm (light/sound) has the same issue. Which is a bit scary.

Thanks in advance!

If the gauge is VDO, using a dual-station VDO sender would probably be about as good as any, maybe better than most. VDO customer service is very responsive. Get gauge info and then ask VDO what senders best match.

-Chris

Thanks Chris, I agree that VDO is very responsive.

However, VDO does not offer a 1/2 NPT dual station sender, and has said that the installed sender must be an OEM part, i.e. Cummins.
But Cummins doesn't offer a 1/2 NPT dual station either.

Hence the dilemma.

The current work around has been to disconnect the upper gauage, this results in correct readings at the lower gaugr.

best
NornaJ

Call Lauderdale Speedometer and Compass and ask for Jay. He is a font of knowledge of instruments and sensors and is very willing to give advice. Also their parts prices are very reasonable: $30 for a sender instead of $100 and $100 for gauges instead of $240.

We were able to improve accuracy of my water temp gauges from 35 degrees above actual temp on a pyrometer to 6 degrees by changing sensors.

Thank you. Will do.

NornaJ said:

Thanks Chris, I agree that VDO is very responsive.

However, VDO does not offer a 1/2 NPT dual station sender, and has said that the installed sender must be an OEM part, i.e. Cummins.
But Cummins doesn't offer a 1/2 NPT dual station either.

Hence the dilemma.

The current work around has been to disconnect the upper gauage, this results in correct readings at the lower gaugr.

Click to expand...

Seems odd. Our Cummins-certified diesel guy here tells me most Cummins engines are delivered with VDO senders.

Anyway... maybe another solution is to use a different port in the oil gallery, install a separate single-station sender there, and wire it to your upper gauge.

??

Edit: Oooops, wait, I was thinking oil pressure. Don't know if there are different ports for coolant sensors; maybe worth a check, though?

-Chris

How about using an adapter going from 1/2 inch to 3/8"?

Depending on the length/depth of the bulb on the sending unit, a 1/2" NPT to 1/4" or 3/8" NPT Brass Reducer Bushing should work. Some of the VDO universal sending units include a set of them, so they should be a reliable way of adapting the VDO sensors to your engine.

Something like this should do it I would think.

https://www.amazon.com/uxcell-Threa...ucer+bushing&qid=1560882508&s=gateway&sr=8-18

or this

https://www.amazon.com/NIGO-Brass-F...4+npt+1/2+npt&qid=1560882152&s=gateway&sr=8-2

I would want to separate senders just in case one fails. I have replaced many senders across the boat and auto world. I don't trust them, even the name brand units. I keep replacements on hand for some of my stuff.

Thanks, everyone
The best solution seems to be a VDO 3/8 sensor with bushing to accommodate the 1/2 inch thread in the coolant head.
Will see if the sensor is sufficiently low and tap out the bushing thread if necessary.
best
NornaJ

Woodland Hills said:

Call Lauderdale Speedometer and Compass and ask for Jay. He is a font of knowledge of instruments and sensors and is very willing to give advice. Also their parts prices are very reasonable: $30 for a sender instead of $100 and $100 for gauges instead of $240.

We were able to improve accuracy of my water temp gauges from 35 degrees above actual temp on a pyrometer to 6 degrees by changing sensors.

Click to expand...

X2 on Lauderdale Speedo.